HID lighting

HID lamps make light with an electric arc through gas in a sealed tube, and they need a ballast to run. The Pacific Northwest National Laboratory notes that much exterior lighting was provided by HID lamps that are difficult to dim or to turn on and off because of long restart times.

That slow restart is one reason sites move to LED, which can dim and respond to sensors. A retrofit plan covers poles, fixtures and controls. See parking lot lighting repair and retrofit.